Guide to the Gish Mine Area
Route
Start point
Big Timber, Montana
End point
Gish mine
Roads
Montana 298, U.S. Forest Service Road 212, unnamed dirt road
Total distance
31.9 miles
Geology
Summary
The Gish mine is located in the Boulder River valley near the west end of the Stillwater Complex. At Gish, the Peridotite zone of the Ultramafic series is exposed, and features of particular interest include an excellent exposure of discordant dunite and a major chromite seam which has been correlated with the G chromitite elsewhere in the complex. Other notable features include: (1) cyclic units which exhibit some lateral variation, and (2) a possible unconformity that separates the series of cyclic units (olivine-bronzite cumulates and bronzite cumulates), which the discordant dunite intrudes, from the major series of olivine cumulates which enclose the main chromite seam.
Key Lithologic Features
- Madison Limestone
- Stillwater Complex rocks: bronzite cumulate, olivine-bronzite cumulate, discordant dunite, chromite seam, and olivine cumulate
Structures
Landforms
Boulder River Falls (in Madison Limestone)
Other Features
Reference
Nicholson, S.W., and Lipin, B.R., 1985, Guide to the Gish Mine Area,
in Czamanske, G.K., and Zientek, M.L., eds.,
The Stillwater Complex, Montana: Geology and Guide : Montana Bureau of Mines and Geology Special Publication 92, p. 358-367.
Availability
Order from the Montana Bureau of Mines and Geology. Search for
this publication's record at the MBMG for ordering information.
